Under the rules of the Federal Communication Commission, by the year 2006, television broadcasters are required to transition from current National Television System Committee (NTSC) antenna systems to digital television (DTV) antenna systems. NTSC antenna systems are analog systems, and during operation of analog NTSC systems only one television transmission signal is transmitted per channel.
DTV is a new type of broadcasting technology. DTV antenna systems transmit the information used to make television pictures and sounds by data bits, rather than by waveforms, as performed by NTSC systems. With DTV, broadcasters will be able to provide television programming of a higher resolution and better picture quality than what can be provided under the current analog NTSC antenna systems. In addition, DTV broadcasters will be able to transmit more than one signal per channel, and thus, deliver more than one television program per station.
All current analog TV broadcasts will be phased out by the end of 2006. During the transition to DTV, television broadcasters are faced with having to transmit on two channels simultaneously, (NTSC and DTV).
Historically, panel antennas are utilized for multi-channel, wideband/broadband applications. One disadvantage of panel antennas is that they exhibit higher windloads than conventional single channel antennas, such as the slotted coaxial type, due to the size of the panel assemblies attached to an antenna mast. Further, the size of the panel antennas limit the amount of radiating assemblies that can be positioned around a mast, and consequently, the amount of flexibility in varying the overall azimuth pattern of panel antennas.
Wideband cavity-backed antennas are also utilized for multi-channel broadband applications. However, there are disadvantages associated with wideband cavity-backed antennas. For example, one conventional waveguide cavity-backed antenna utilizes a radiator element having a “T-shaped” geometry. The “T-shaped” radiator element is costly to manufacture because a significant amount of machining labor is required to construct the “T-shaped” radiator element.
Further, the design of the conventional wideband cavity-backed antenna is such that the assembly of the waveguides form the antenna mast-like structure, without use of a mast. The design also includes a feed system that is positioned within the hollow space formed when the waveguides are assembled together.
However, one drawback of the conventional wideband cavity-backed structure is that when the feed system requires service, the antenna has to be removed from its supporting structure and disassembled to access the feed system. Accordingly, interruption in television service to customers who are receivers of television signals transmitted by the antenna requiring service is prolonged by the time required to take down and disassemble the antenna to reach the feed system.
Further, the design of the conventional wideband cavity-backed antenna requires a capacitive disk, which is coupled to the “T-bar shaped” radiator element and separated from the waveguide by an air gap, along with a grounding rod to match the impedance of the transmission line to the impedance of the radiator element.
However, the air gap limits the amount of power that the radiator element is able to accommodate. The air gap, like a dielectric, is only able to accommodate a limited amount of power without breaking down. If the air gap breaks down and allows current to flow between the transmission line and the waveguide, the undesired current could potentially damage the radiating element.
Accordingly, it would be desirable to provide an antenna that may be utilized for multi-channel, broadcast applications that exhibits low windloads.
It would also be desirable to provide an antenna that allows for greater flexibility in varying the overall azimuth pattern of the antenna.
In addition, it would also be desirable to provide a multi-channel, broadband antenna that has high power handling capabilities.
Further, it would be desirable to provide a multi-channel, broadband antenna that allows for simplicity in impedance matching.
Moreover, it would be desirable to provide a multi-channel, broadband antenna that is cost-effective to manufacture and simple to service.